Ultra Fine Threads
Ultra Fine Threads
(OP)
Does anybody have experience analyzing ultra fine threads for shear?
I have specified a 1/4-127UN thread screw that is to compress a die-spring with a force of around 250N (60lb). Someone is sure to ask me how strong this is. There is not chance of compression failure, but I would wonder how accurate the threads are, relative to the nominal profiles.
I have specified a 1/4-127UN thread screw that is to compress a die-spring with a force of around 250N (60lb). Someone is sure to ask me how strong this is. There is not chance of compression failure, but I would wonder how accurate the threads are, relative to the nominal profiles.
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JHG





RE: Ultra Fine Threads
RE: Ultra Fine Threads
RE: Ultra Fine Threads
Mike Halloran
Pembroke Pines, FL, USA
RE: Ultra Fine Threads
You mean differential threads. M5×0.8 works very well against 10-32UNF.
I have tried that. They did not like it. This is an optical fixture, and all sorts of ultra-precision threads are available off the shelf. My problem is that I need a pre-load spring. The extension springs that fit in your system are not very stiff. I have figured out how to install medium strength stripper plate die-springs, which are stiff, and provide quite a lot of travel for their height. The 1/4-127UN screws should work okay, but I am wondering about their shear strength.
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JHG
RE: Ultra Fine Threads
Analytically, the finer the thread, the closer the pitch diameter is to the outer diameter, so the larger it is. The bending moment is similar because teeth shorten in proportion to the pitch. Presumably the tolerance is proportional to the pitch, so the loss due to clearance is the same overall regardless of size.
What was unliked about the differential screw setup?